<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
  var user={}
  user.name = 'John';
  document.write("name:"+user.name+'<br/>');
  user.surname = 'Mike';
  document.write("surname:"+user.surname+'<br/>');
  user.name = 'Peter';//// 'Peter' - edited
  document.write("名字被修改为"+user.name+'<br/>');
  delete user.name;
  document.write(user.name+'<br/>');
</script>
</body>
</html>